A wide variety of organic photochromic dyes have been developed in recent years, and dyes available as commercial products are increasing constantly. These have been extensively applied to eyeglass lenses in the general market trend toward plastic. Currently, plastic photochromic lenses in which organic photochromic dyes have been applied are currently being marketed for use in eyeglasses.
These plastic photochromic lenses develop color in the bright outdoors to produce the same antiglare effect as high-density color lenses, but return to high transmittance when moved indoors. However, a more rapid response is demanded. Currently, several tens of minutes are required to return to pre-coloration transmittance from a state in which color has been fully developed. When compared to the coloration process, which reaches a state of high coloration in about one minute, the fading rate is extremely slow and requires improvement.
The coloration reaction is highly dependent on the inherent characteristics of photochromic dyes resulting from their molecular structures, and is known to be greatly, affected by the polymer matrix in which the dyes are present. Plastic photochromic lenses are generally manufactured by dissolving a photochromic dye in a mixture of monomers followed by mold casting polymerization. Methacrylic monomers are desirably employed as the monomers. Further, photochromic properties vary greatly based on the composition of the mixture of methacrylic monomers. Accordingly, it has been found that a rapid photochromic reaction is attained by the simultaneous use of monofunctional or bifunctional monomers and short-chain trifunctional or greater monomers to the extent that the basic properties such as transmittance, photoresistance, strength, thermal resistance, and cutting and grinding processability required of eyeglass lenses are achieved.
Further, resistance to abrasion is imparted to the plastic lenses generally employed in eyeglasses by means of a multifunctional acrylate or methacrylate ultraviolet-curing film or silicone or melamine thermosetting film applied to the plastic substrate surface. Of these, organopolysiloxane hard films obtained by thermosetting are the most widespread. Since these hard films exhibit high adaptability with the diethylene glycol bisallyl carbonate resin and polythiourethane resins that are currently employed as the mainstream eyeglass substrate resins and can be made to adhere well to the substrate resin by a simple pretreatment in the form of immersion in an alkali aqueous solution, they are currently widely employed in the trade. Metal colloids are often incorporated into the film component of organopolysiloxane cured films to significantly improve the basic performance of the hard surface film, such as resistance to abrasion and photoresistance.
However, substrates of methacrylic resin generally tend not to adhere well to the above-mentioned organopolysiloxane hard films, and the introduction of metal colloids further disrupts adhesion. Further, the introduction of trifunctional and above monomers that effectively improve the coloration reaction of photochromic lenses as substrate resin components is known to sharply decrease adhesion. Thus, in combinations of methacrylic substrate resins employing polymerization components in the form of trifunctional or above monomers and hard surface films comprising metal colloids, simply immersing in the above-mentioned alkali aqueous solutions does not yield the practical adhesion required of eyeglass lenses.
Accordingly, a number of means other than pretreatment with chemicals such as alkali aqueous solutions are conceivable for improving adhesion when a polyorganopolysiloxane hard surface film comprising a metal colloid is provided on a methacrylic substrate resin employing a trifunctional or greater monomer as a polymer component. For example, general methods include physically edging the surface by rubbing cloth, paper, or a sponge containing an abrasive against the substrate resin, providing an adhesive layer of polyurethane or the like between the substrate resin and hard film, and treating the substrate resin with plasma.
However, eyeglass lenses come in an extremely large variety of magnifications and designs. The method of physically edging the surface by rubbing the substrate resin with cloth, paper, or sponge containing an abrasive is difficult to apply uniformly, reliably, and in large quantity, creating problems in manufacturing efficiency.
Further, in the method of providing an adhesive layer between the plastic lens substrate and the hard film, both the adhesive layer and the hard film must be coated, dried, and thermoset in cumbersome steps. During these operations, the potential for contamination with foreign matter increases. When a hard film is provided on a soft adhesive layer, surface hardness tends to decrease relative to when no intermediate adhesive layer is provided.
In the method of plasma treating the substrate resin, the result tends to be influence by the composition of the substrate resin. In substrate resins comprising trifunctional or greater monomers, there is a problem that accomplished improvement in adhesion is inadequate.
Accordingly, the present invention, devised to solve the above-stated problems of conventional art, has for its object to provide both a means of imparting adequate adhesion even to hard surface films comprising highly concentrated metal colloids in methacrylic resin lenses comprising trifunctional or greater monomers, thereby providing plastic photochromic lenses having hard surface films with rapid color fading reaction speed, good resistance to abrasion, and good adhesion, and a method of manufacturing the same.